I. Field of the Invention
This invention relates to the incubation and hatching of eggs under artificial conditions such as exist in commercial incubators and hatchers. More particularly, it relates to the artificial incubation and hatching of eggs in incubators and hatchers wherein a very large number of eggs are placed in the incubator at the same time for incubation and all hatchlings are removed from the hatcher at the same time. The hatchlings are removed from the hatcher at the expiration of an optimal incubation period. The optimum incubation period is presumed to expire after that period of time when most of the eggs have hatched, and beyond which period of time further delay in the removal of the hatchlings to permit hatching of the remaining eggs would result in keeping hatchlings in the hatcher beyond a period of time they can endure, such that they will suffer dehydration, stress or possibly death before their removal.
II. Description of Related Art Including Information Disclosed Under Sections 1.97 and 1.98
As previously set forth, in commercial incubators of the type wherein a large number of eggs are placed on a tray and a large number of trays are placed on a rack which is in turn placed in an incubator and then in a hatcher, it is desirable to remove the rack from the hatcher after the expiration of an optimal incubation period. As previously set forth, not all eggs will hatch precisely at or close to the expiration of the optimal hatching period. However, if the removal is delayed, the early hatchlings are subjected to stresses of dehydration by being kept in the confines of the hatching tray for extended periods of time. It not being normally profitable to return eggs which have not yet hatched to the hatcher, those eggs are destroyed with a resultant loss not only of the potential chicks, but also of the profitable use of the space occupied by those eggs in the incubator and hatcher during the incubation period.
It has been found that the incubation periods for individual eggs undergoing artificial incubation exhibit greater variability than do the incubation periods for eggs hatched by an incubating maternal hen. Further, it has been noted that artificially incubated hatchlings are slower to partake of feed and water than are hatchlings incubated and cared for by a maternal hen.
With respect to the commercial artificial incubation and hatching of eggs, the optimum conditions of temperature and humidity have been established and they can now be controlled very precisely in commercial artificial incubators. See U.S. Pat. No. 4,706,608 issued Nov. 17, 1987 for an example of a commercial incubator, see U.S. Pat. No. 5,005,523 issued on Apr. 9, 1991 for an example of such a commercial hatcher. Nevertheless, hatchability under commercial conditions is still well below 100% of the fertile eggs placed in the incubator.
It is known that embryo precocial avian species (precocial refers to species which are born mobile and venture away from the nest as soon as they are born), such as domesticated poultry species, produce a wide variety of sounds toward the end of their incubation period. These sounds include the vocalizations that the hatchling will make as a newly hatched chick. It is also known that these sounds, in a natural situation, may affect the behavior of the incubating parent bird. There is also evidence that the embryos respond to external stimuli at this time. For example, it has been reported that the clucking sound of a brooding hen will stop a domestic chick embryo from giving distress calls and that changing the position of the egg can elicit pleasure twitters from the enclosed embryo.
There is also evidence that an embryo learns before hatching to discriminate between its parents' vocalization and the vocalization of other birds. Calls by an incubating hen pheasant have also been shown to sensitize and pre-dispose embryonic chicks for proper response to calls that they will hear after hatching. This is true for feeding and caution calls as well as other calls such as cock attraction cluck calls and alarm calls.
With respect to commercial artificial incubation, perhaps the most important interaction is that between the embryos in neighboring eggs. It has been shown that the development of embryos of Bob White quail are accelerated if the eggs are incubated for the last few days with their shells in contact with each other. The acceleration of hatching is brought about by the regular loud clicking which is known to begin in domestic fowl and quail about twelve hours before hatching. Further studies have shown the accelerating effects can be produced artificially.